Exoplanets with the Most Earth-like Interiors

This is a list of exoplanets with the most Earth-like interiors ranked by the Interior Earth Similarity Index (iESI), a measure of how an exoplanet size and bulk density compares to Earth (Table 1). These are Earth-size rocky bodies but most are unsuitable for life because they orbit very close to their parent star. Those with iESI values above 0.8 can be considered Earth-like in internal composition.

The list also show the Surface Earth Similarity Index (sESI), a measure of Earth-like surface properties (atmosphere with temperatures closer to 15°C), and the Earth Similarity Index (ESI), an overall measure of Earth-likeness for both interior and surface properties. There was not enough data to calculate the sESI and ESI for some cases.

Some notable exoplanets, from media coverage in the last few years, are highlighted. The only potential habitable exoplanets in the list are Gliese 581 d, HD 85512 b, and Kepler-22 b. Figure 1 shows a plot of sESi vs iESI.

Table 1. List of exoplanets with the most Earth-like interiors (similar size and bulk density as Earth but not necessarily surface temperature). M stands for planet mass and R for radius (some were estimated with mass-radius relationships).

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Name M (EU) R (EU) iESI sESI ESI

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Kepler-20 f 1.03 1.01 1.00 0.20 0.44

Kepler-20 e 0.64 0.87 0.97 0.09 0.29

KOI-55 c 0.77 0.87 0.94 0.00 0.03

Gliese 581 e 2.24 1.25 0.93 0.34 0.57

CoRoT-7 b 4.87 1.68 0.91 0.03 0.16

HD 20794 c 2.79 1.32 0.91 – –

HD 20794 b 3.12 1.37 0.90 – –

HD 215152 b 3.19 1.37 0.90 – –

HD 215152 c 3.56 1.42 0.89 – –

MOA-2007-BLG-192-L b 3.67 1.43 0.89 – –

HD 85512 b 4.04 1.47 0.88 0.72 0.79

HD 39194 b 4.29 1.49 0.87 – –

HD 156668 b 4.81 1.54 0.86 0.13 0.34

HD 40307 b 4.84 1.54 0.86 – –

PSR 1257 12 c 5.17 1.57 0.86 – –

PSR 1257 12 d 5.21 1.57 0.86 – –

55 Cnc e 8.64 2.13 0.85 0.02 0.14

Kepler-18 b 6.92 2.01 0.85 0.06 0.23

HD 20794 d 5.50 1.60 0.85 – –

Kepler-20 b 8.60 1.91 0.85 0.07 0.24

61 Vir b 5.87 1.62 0.85 0.08 0.25

HD 39194 d 5.94 1.63 0.84 – –

Kepler-21 b 6.02 1.64 0.84 0.02 0.14

HD 136352 b 6.09 1.64 0.84 – –

OGLE-05-390L b 6.24 1.65 0.84 – –

Gliese 581 c 6.24 1.65 0.84 0.64 0.73

HD 1461 c 6.83 1.69 0.83 0.13 0.33

HD 39194 c 6.86 1.70 0.83 – –

Gliese 581 d 6.97 1.70 0.83 0.59 0.70

HD 154088 b 7.08 1.71 0.83 – –

Kepler-10 b 4.57 1.42 0.83 0.02 0.12

HD 215497 b 7.34 1.73 0.83 – –

Gliese 433 b 7.41 1.73 0.82 – –

HD 40307 c 7.93 1.76 0.82 – –

Gliese 3634 b 8.16 1.78 0.82 0.25 0.45

Gliese 876 d 8.71 1.81 0.81 0.21 0.42

HD 181433 b 8.73 1.81 0.81 – –

HD 1461 b 8.77 1.81 0.81 0.07 0.24

Kepler-9 d 6.99 1.65 0.81 0.03 0.15

HD 93385 b 9.65 1.86 0.80 – –

CoRoT-7 c 9.69 1.86 0.80 0.08 0.25

Gliese 176 b 9.72 1.86 0.80 0.37 0.54

PSR 1257 12 b 0.03 0.33 0.75 – –

Kepler-11 b 4.30 1.98 0.75 0.12 0.30

KOI-730 e 4.14 2.02 0.72 0.10 0.27

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Figure 1. Plot of sESI vs iESI for the 716 confirmed exoplanets so far. Those with sESI and iESI values above 0.8 are labeled.